Morphology controlled syntheses of Cr doped ZnO single-crystal nanorods for acetone gas sensor

•In the synthesis Cr3+ ion was used as a dopant and a morphology controller.•Cr–ZnO sensor exhibits higher response and better selectivity.

In this study, highly crystallized hexagonal prism-like ZnO nanorods with planar tips and pyramid tips were successfully fabricated by hydrothermal method. The morphology and structure of samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive spectrometer (EDS), Brunauer–Emmett–Teller (BET), scanning electron microscope (SEM) and transmission electron microscope (TEM). XRD and XPS analyses indicate Cr3+ ions are successfully doped into the ZnO lattice. In hydrothermal process, Cr ions replace the Zn sites and activate the ±{101¯1} crystal facets. Thus the morphology of ZnO is hexagonal prisms with planar tips, while the morphology of Cr doped ZnO is hexagonal prisms with pyramid tips. Sensing behavior of the sensors is also investigated. The response of Cr–ZnO sensor is 104 to 100 ppm acetone at 300 °C, which is four times higher than that of ZnO sensor. Improved response and selectivity of the sensor is attributed to the increase of electron concentration, which is optimized by Cr doping.

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